The field to which this invention relates is known as Electrical Discharge Machining, hereinafter sometimes referred to as EDM, in which material is removed from an electrically conductive workpiece by the action of the electrical discharges passing between a tool electrodes and the work. A dielectric liquid coolant is circulated through the machining gap which is maintained between the electrode tool and the workpiece during machining operation. A servo feed system is included to provide for relative movement between the workpiece and the electrode tool to maintain optimum gap spacing as workpiece material is progressively removed. In the EDM operation, the electrode is always maintained in spaced relationship with the workpiece.
In order to conduct electrical discharge machining with reliable and predictable results, an electrical discharge machining circuit of the independent pulse generator type is preferably used to provide machining power pulses of precisely controllable frequency and on/off time. In a particular type of EDM circuit, the pulse generator may be embodied as a multivibrator, oscillator or the like. One type of pulse generator suitable for use in conjunction with this invention is shown and described in U.S. Pat. No. 3,854,026 issued on Dec. 4, 1974 to Oliver A. Bell, Jr. et al for "GATED TIMING SYSTEM FOR ELECTRICAL DISCHARGE MACHINING", which patent is of common ownership with the present application. A servo feed system for electrical discharge machining is shown and described in U.S. Pat. No. 3,727,024 issued on Apr. 10, 1973 to Oliver A. Bell for "ELECTRICAL DISCHARGE MACHINING SERVO CONTROL CIRCUIT" also of common ownership herewith. The present invention represents an advancement in a feed system in which the servo feed circuit is stabilized in its operation.